1. Field of the Invention
The present invention relates to improvement of a disc device including an optical pickup feed mechanism for reciprocating an optical pickup in the radial direction of a disc by a threaded shaft (screw shaft).
2. Description of the Related Art
Conventionally, there are known disc devices which include an optical pickup feed mechanism for reciprocating an optical pickup between the inner peripheral side and the outer peripheral side of a disc in the radial direction thereof.
The optical pickup feed mechanism includes, for example, a threaded shaft, which is threaded with a screw portion formed on an optical pickup main body and reciprocates the optical pickup main body in the radial direction of a disc while supporting it, a guide shaft, which is disposed in parallel with the threaded shaft and guides the optical pickup main body in the radial direction while supporting it, a rotating drive source, that is, a motor for reciprocating the optical pickup main body, and a rotation transmission gear, which is fixed to an end of the threaded shaft and transmits the rotation of the motor to the threaded shaft.
In this type of disc device, when the discs are DVD discs and the like, address read error may occur, and a CLV error which results from a spindle being out of synchrony for at least a predetermined period of time, while information recorded on the recording surfaces of the discs is read. These errors are generally called xe2x80x9cservo errorsxe2x80x9d.
When this type of the servo error occurs, there is a high probability that the objective lens of an optical pickup will be away from the recording surfaces of the discs and will be located on a mirror surface. To cope with this problem, conventionally, the threaded shaft is rotated so as to move the optical pickup by carrying out servo error processing as shown in the flowchart in FIG. 7 so that the objective lens will be located on the recording surface.
For example, when the servo error occurs in the DVD disc, disc stop processing is carried out to stop the rotation of the disc (S.1), it is determined whether the servo error is the address read error or the CLV error (S. 2), when the servo error is the address read error or the CLV error, an ordinary voltage (for example, 2.4 V) is imposed on the motor as the rotating drive source to rotate the threaded shaft (S. 3), and it is determined whether a limit switch, which determines whether the optical pickup main body is located on the mirror surface on the inner peripheral side of the disc or on the mirror surface on the outer peripheral side thereof, is turned on or off (S. 4).
The limit switch is arranged such that it is turned on, for example, only when the optical pickup main body is located on the mirror surface on the inner peripheral side of the disc and is turned off when the optical pickup main body is located at a position nearer to the outer peripheral side than the mirror surface.
A microcomputer for controlling the operation of the disc device starts a 500 ms timer when the limit switch is turned on (S. 5), rotates the threaded shaft in a forward direction (S. 6), moves the optical pickup main body to the outer peripheral side of the disc and determines whether or not the limit switch is turned off (S. 7), stops the rotation of the threaded shaft when the limit switch is turned off (S. 8), and restarts the disc (S. 9). When the limit switch remains turned off at step S. 7, the process goes to step S. 10 where it is determined whether or not 500 milliseconds have passed (S. 10). When 500 milliseconds have not passed, the process returns to step S. 6 and performs the same processing, whereas when the 500 milliseconds have passed, the process goes to step S. 8, stops the rotation of the threaded shaft and restarts the disc (S. 9)
When it is determined at step S. 4 that the limit switch is turned off, it is determined that the optical pickup main body is not on the mirror surface on the inner peripheral side of the disc and the 500 ms timer is started (S. 11). Then, the threaded shaft is rotated in a reverse direction (S. 12), the optical pickup main body is moved to the inner peripheral side of the disc and it is determined whether or not the limit switch is turned on (S. 13). When the limit switch is turned on, the process goes to step S. 8, and after the rotation of the threaded shaft is stopped, the disc is restarted (S. 9), it is determined whether or not the 500 ms have passed when the limit switch remains turned off (S. 14). When 500 ms have passed, the process returns to step S. 12 and performs the same processing. Note that when an error other than the address read error and the CLV error is caused at step S. 2, the process goes to step S. 9 and restarts the disc.
In the conventional optical pickup mechanism, however, when the disc device is used in the environment of the compartment of a passenger car and the like, biting may be caused between the optical pickup main body and a rotation transmission gear fixed to an end of the threaded shaft or between the optical pickup main body and the other end of the threaded shaft by the servo error such as by the overrun of the threaded shaft due to being out of track while the information of a disc is read which is due to the influences of vibration and the like, the excessive approach to a mirror surface caused by a count error in the number of tracks during access, and the like. When the biting arises, a disadvantage results in that the biting cannot be removed even if an ordinary voltage is imposed, the optical pickup is continuously out of the recording surface of the disc and servo cannot be easily applied.
To avoid the biting, it is contemplated to arrange an optical pickup mechanism as a structure which does not cause the biting. When such a structure is employed, however, there is problems in that the structure becomes complex and cost is increased or a disc device is increased in size.
An object of the present invention, which was made in view of the above circumstances, is to provide a disc device which can remove the biting of an optical pickup main body, which is threaded with a threaded shaft and reciprocated in the radial direction of a disc, at an end of the threaded shaft by software and can reliably remove the biting of the optical pickup main body at the end of the threaded shaft without increasing cost and the size of the device as a whole.
In accordance with the present invention, there is provided a disc device comprising: an optical pickup feed mechanism for effecting reciprocal movement of an optical pickup between the inner peripheral side and the outer peripheral side of a disc in the radial direction thereof, the optical pickup feed mechanism including a threaded shaft for screwing engagement with a thread portion formed on an optical pickup main body for effecting the reciprocal movement of the optical pickup main body in the radial direction of the disc while supporting the optical pickup main body, a rotating drive source for causing the reciprocal movement of the optical pickup main body, and a rotation transmission gear fixed to an end of the threaded shaft for transmitting the rotation of the rotating drive source to the threaded shaft; a biting determination means for determining the biting of the optical pickup main body at an end of the threaded shaft; and a biting removal means for rotating the rotating drive source in such a direction as to remove the biting 6f the optical pickup main body when the biting determination means determines that the optical pickup main body is bitten.
According to the present invention arranged as described above, it is preferable that the biting of the optical pickup main body be determined by software.
It is preferable that the rotating drive source be a motor and that the biting removal means include a high voltage imposing means for imposing, when the biting of the optical pickup main body is not removed, a high voltage which is higher than an ordinary voltage which is imposed on the motor to reciprocate the optical pickup main body by the threaded shaft.
According to the above arrangement, since the biting is removed by imposing a voltage higher than the ordinary voltage, the biting can be reliably removed.
It is preferable that the high voltage imposing means increase the high voltage stepwise.
According to the above arrangement, the circumstances in which the biting is caused again by the execution of the biting removing processing can be avoided.
It is preferable that the high voltage imposing means vary a period of time, during which the high voltage is imposed, stepwise.
According to the above arrangement, the biting can be easily removed because an impact is applied in rotation by imparting variation to the period of time during which the high voltage is imposed.
It is preferable that the biting removal means include a biting removal determination means for determining whether or not the biting of the optical pickup main body is removed.
According to the above arrangement, whether or not the biting is removed can be reliably determined.
It is preferable that the biting removal determination means include one set of a limit switch for determining whether the optical pickup main body is located on the inner peripheral side or on the outer peripheral side of the disc in the radial direction thereof.
It is preferable that the biting removal determination means determine whether or not the biting is removed in a different period of time depending upon whether the biting occurs on the inner peripheral side of the disc or on the outer peripheral side thereof.
According to the above arrangements, the removal of the biting can be determined using an existing limit switch.
It is preferable that the biting removal determination means have a waiting time until the ordinary voltage is imposed after the high voltage is imposed.
According to the above arrangement, an unintended movement of the optical pickup main body, which is caused by instantly imposing the ordinary voltage on the rotating drive source after the removal of the biting, can be prevented.